Linear copolyester elastomers having been described heretofore, as for example, in U.S. Pat. No. 3,766,146 prepared, illustratively, by catalytic reaction of a mixture of reactants comprising, illustratively, poly(tetramethylene ether glycol), 1,4-butanediol and dimethyl terephthalate. The copolyesters so prepared contain elevated percentages of reactant ether glycol component.
The preparation of polyalkylene terephthalatepolyether block copolymers in situ is described in Netherlands patent No. 141,919. However, the product polymers incorporate in excess of 10 percent by weight of polyether.
These higher proportions of polyether, while imparting certain desirable properties to the resulting polymer, do so frequently at a sacrifice of certain of the more desirable properties such as the elevated melting point had by the corresponding terephthalate homopolymer.
If a copolymer could be economically produced retaining the advantages of the homopolymer, poly(tetramethylene terephthalate), including retention of its melting point, while securing significantly enhanced heat distortion properties, high strength engineering thermoplastic resins would result having not only excellent moist high temperature electrical properties, as well as low creep characteristics, but would be suitable for enhanced use as, illustratively, gaskets or other sealant means for use in connection with automobile engines and the like while manifesting improved mold fill and process propensities and a significant advance in the state of the art would, as a result, be achieved.